The liter (L) is the most widely used metric unit of volume, equal to 1,000 cubic centimeters or one cubic decimeter, serving as the standard for beverages, fuel, and household liquids worldwide. Gasoline prices, bottled water, and milk cartons all reference liters in most countries. One liter equals approximately 1.0567 US quarts or 0.2642 US gallons.

The US gallon (gal) is an imperial volume unit equal to exactly 3.7854 liters, the standard measurement for fuel, milk, and paint in the United States. Gasoline prices at American pumps are always quoted per gallon, and US vehicle fuel efficiency is measured in miles per gallon. One US gallon equals 4 US quarts or 8 US pints.